Ty and delta elements are dispersed repeated sequences inserted throughout the yeast genome that are often associated with genetic rearrangements. Tys are transposable elements similar to retroviruses, and deltas are analogous to long terminal repeats. The prevalence of Tys and deltas, and the high levels of recombination involving these portable regions of homology, indicate that this recombination is probably very important in the evolution of the yeast genome. The rules governing this recombination may be identical to general recombination, there may be specific controls adapted for dispersed repeated sequences, or there may be some delta and Ty specific effects. For example, the reverse transcribed free Ty DNA circles or a delta specific endonuclease may be involved in delta recombination events. The long-term objective of the proposed research is to determine the mechanisms involved in Ty and delta recombination and to study and the genes that control this recombination. Sequences analogous to Tys and deltas exist in a large number of eukaryotes, including man and are often associated with disease. Therefore, it is hoped that some of the results of these studies may have a general significance. Interesting Ty and delta promoted rearrangements will be characterized at the sequence level. Strain specific effects that drastically alter the frequency and types of Ty and delta associated rearrangements will be investigated. The effect of the recombination deficient mutation, rad52-, on the types of recombination that occur between repeated Tys, deltas, and non-transposable sequences will be examined. Finally, since misreading has been implicated in the expression of Ty encoded genes, the effect of translational misreading on the rate of Ty transposition will be examined.